JP2633057B2 - Silicon single crystal manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for producing a large-diameter silicon single crystal by the Czochralski method.

[Prior Art] In the LSI field, the diameter required for silicon single crystals is increasing year by year. Today, state-of-the-art devices use silicon single crystals with a diameter of 6 inches. It is said that a silicon single crystal having a diameter of 10 inches or more, for example, a silicon single crystal having a diameter of 12 inches will be required in the future.

There are two methods for producing a silicon single crystal by the Czochralski method (CZ method). A method of rotating the crucible and a method of not rotating the crucible. Today, all silicon single crystals used for LSI are manufactured by rotating the crucible and the silicon single crystal in opposite directions, and heating the crucible with an electric resistance heater surrounding the side of the crucible. Being manufactured. Despite many attempts, silicon single crystals with a diameter of 5 inches or more have never been made by a method that does not rotate the crucible, or a heating method other than the above (electric resistance heating body), and will be made in the future Never. The reason is that without the rotation of the crucible, or by other heating methods such as electromagnetic induction heating or electric resistance heating from the bottom of the crucible, a complete concentric temperature distribution can be obtained for the growth of the silicon single crystal. Because there is no. Silicon single crystal growth is very sensitive to temperature.

In the CZ method in which the crucible rotates (hereinafter referred to as a normal CZ method), strong convection occurs in the silicon melt due to the crucible rotation and electric resistance side heating, and the silicon melt is well stirred. As a result, it is desirable to grow large diameter silicon single crystals having a diameter of 5 inches or more, ie, a uniform and completely concentric melt surface temperature distribution with respect to the silicon single crystal is obtained.

As described above, there is a great difference in the flow of the silicon melt between the normal CZ method and other CZ methods. This difference results in a large difference in the growth conditions of the silicon single crystal. Furnace parts (eg hot zone, crucible, partition member, etc.)
Also differs greatly between the two. The concept of silicon single crystal growth is completely different between the two.

In the ordinary CZ method, the silicon melt in the crucible decreases as the silicon single crystal grows. Then, as the silicon single crystal grows, the dopant concentration in the silicon single crystal increases, and the oxygen concentration decreases. That is, the properties of the silicon single crystal fluctuate in the growth direction. As the density of LSIs increases, the quality required for silicon single crystals has become more stringent year by year.

As means for solving this problem, the silicon melt in a quartz crucible of the ordinary CZ method is partitioned by a cylindrical quartz partition member having small holes, and while the raw material silicon is supplied to the outside of the partition member, the partition member is separated. There is known a method of growing a columnar silicon single crystal inside a substrate (for example, Patent Publication 40-40184 P1 L20-L35).

As pointed out in Japanese Patent Application Laid-Open No. 62-241889 (P2 L12-L16), a major problem of this method is that solidification of the silicon melt easily occurs inside the partition member starting from the partition member. The cause is as follows. As is clear from the fact that the partition member made of quartz is used for an optical fiber, heat is well transmitted by radiation. That is, the heat in the silicon melt is transmitted upward through the partition member as light, and is radiated from a portion of the partition member exposed on the silicon melt surface. Therefore, in the vicinity of the partition member, the temperature of the silicon melt is greatly reduced. In addition, normal CZ
In the method, the surface temperature of the silicon melt is uniform and directly above the solidification temperature due to strong stirring of the silicon melt. These two things overlap and the surface of the silicon melt in contact with the partition member is in a state of being very easily solidified.
Japanese Patent Laid-Open Publication No. Sho 62-241889 proposes a method that does not use a partition member in order to avoid this problem. However, in this method, since the raw material melting portion is narrow, the raw material melting ability is extremely small, and it is impossible to supply the raw material silicon in an amount corresponding to the amount of silicon single crystal pulled.

Japanese Unexamined Patent Publication No. 1-153589 proposes a method of using a partition member and preventing solidification therefrom in order to be able to supply the raw material silicon in an amount corresponding to the amount of silicon single crystal pulled. This patent proposes to completely cover the partition member with a heat shielding member. With this method, heat dissipation from the partition member can be prevented. Therefore, the raw material silicon is supplied in an amount corresponding to the amount of silicon single crystal pulled, and solidification is prevented from occurring.

[Problems to be Solved by the Invention] According to the method of Japanese Patent Application Laid-Open No. 1-153589, an amount of raw material silicon is supplied in an amount corresponding to the amount of silicon single crystal pulled,
In addition, the occurrence of solidification can be prevented. However, when the crystal pulling speed is increased to improve the productivity, the supply amount of the raw material silicon must be increased accordingly. Since the temperature of the raw material melting section decreases as the raw material silicon supply amount increases, the method of growing the silicon single crystal while supplying the raw material in an amount corresponding to the pulling amount of the silicon single crystal has an upper limit naturally in the pulling speed. . Although the upper limit of the pulling speed varies depending on the configuration of the silicon single crystal apparatus, the inventors have studied and found that in the method of JP-A-1-153589, the pulling speed was 1 mm / min for a crystal having a diameter of 6 inches.
As described above, it was found that solidification occurs from the outside of the partition member due to a decrease in the temperature of the raw material melting section. Therefore, in the method of JP-A-1-153589, the crystal pulling speed is 1 mm / min.
In order to maintain the above, some means must work.

The present invention has been made in view of the above circumstances, and in a silicon single crystal manufacturing apparatus that continuously supplies an amount of raw material silicon corresponding to the amount of silicon single crystal pulled up, solidification from a partition member compared to a conventional apparatus. Prevent occurrence,
It is intended to improve the upper limit of the crystal pulling speed.

[Means for Solving the Problems] A silicon single crystal manufacturing apparatus according to the present invention includes a rotating quartz crucible containing a silicon melt, a graphite crucible supporting the quartz crucible, and a side view of the graphite crucible. An electric resistance heating body to be heated, a quartz crucible member having a small hole through which a silicon melt is divided into a single crystal growing section and a raw material melting section in the quartz crucible and a silicon melt can flow, and the partition member; In a silicon single crystal manufacturing apparatus having a heat retaining cover for covering the raw material melting section and a raw material supply apparatus for continuously supplying raw silicon to the raw material melting section, a silicon molten liquid level above a cylindrical portion of the graphite crucible is provided. From the position corresponding to 50 mm below the silicon melt surface
A plurality of openings are provided in a range up to a position corresponding to 20 mm.

[Operation] When the supply amount of the raw material silicon is increased, the solidification occurs outside the partition member, that is, at the raw material melting portion, because the temperature gradient of the silicon melt in the crucible radial direction is small. This is because the heat energy input from the side of the silicon melt is taken by the supplied raw silicon, and the temperature of the raw material melting section is lowered.

The pulling speed of the silicon single crystal is determined by the total amount of heat reaching the crystal solidification interface from the lateral direction and the lower direction in the silicon melt. Therefore, in the case of the same lifting speed, it is better to increase the ratio of the heat input from the side direction in the silicon melt, that is, to increase the temperature gradient in the crucible radial direction, so that the solidification from the partition member Is unlikely to occur. In the apparatus for manufacturing a silicon single crystal according to the present invention, the graphite crucible in a portion corresponding to the vicinity of the silicon melt surface is provided with a plurality of openings or more. Direct heat input occurs, increasing the percentage of side heat input. Therefore, solidification from the partition member is less likely to occur than in the conventional apparatus, and the crystal pulling speed can be increased.

In order to examine the vertical range of the opening that can increase the heat input efficiency to the raw material melting part compared to the case where there is no opening in the graphite crucible, a narrow opening with a width of 10 mm in the height direction was set Were placed at various positions, and a silicon single crystal growing experiment was performed. As is apparent from FIG. 3, the maximum pulling speed that can be lifted while preventing solidification from the partition member is smaller than 20 mm below the silicon molten liquid level as compared with the case where there is no opening. This is because the heat input from the electric resistance heating body to the silicon melt changes from the side heat input trend to the downward heat input trend as the opening is positioned lower with respect to the silicon melt surface. That is, the temperature gradient in the crucible radial direction is reduced, and solidification from the partition member is likely to occur. It was also found that the opening contributed to the improvement of the maximum pulling speed at the opening near the surface of the silicon melt, and had little effect above 50 mm above the surface of the silicon melt.

Example An example of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an apparatus for manufacturing a silicon single crystal having a diameter of 6 inches according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a plurality of openings of a graphite crucible according to an embodiment of the present invention. In the drawings, (a) is a diagram showing one embodiment of the present invention, and (b) is another embodiment of the present invention. 1 is a quartz crucible having a diameter of 20 inches, which is set in a graphite crucible 2. The cylindrical portion of the graphite crucible 2 has a plurality of openings 22. This opening 22
Has a size corresponding to a range of 40 mm or less above the silicon melt surface and 5 mm or more below the silicon melt surface. That is, the number of the openings is 20 at an opening having a diameter of 45 mmΦ. This opening
22 directly inputs heat from the electric resistance heating body to the silicon melt 7, and the heat input to the side of the crucible increases. The graphite crucible 2 is supported by a pedestal 4.
The pedestal 4 is connected to an electric motor outside the furnace, and serves to impart a rotational movement (10 rpm) to the graphite crucible 2. Reference numeral 7 denotes a silicon melt placed in the crucible 1. From now on, the columnar silicon single crystal 5 rotates (20 rpm)
While being pulled up at a speed of 1.2 mm / min. Reference numeral 3 denotes an electric resistance heating body surrounding the graphite crucible.

Atmospheric gas is introduced into the furnace from the lifting chamber 20 and finally decompressed by a discharge port 19 at the furnace bottom (not shown).
Is discharged by

Inside the furnace (inside the chamber top lid 16 and chamber body 17)
Is 0.01-0.03 atm. The above is the same as that of an apparatus for manufacturing a silicon single crystal by a normal CZ method.

Reference numeral 8 denotes a partition member made of quartz glass containing high-purity bubbles which is arranged concentrically in the crucible 1. Its diameter is 35cm. A small hole 10 is formed in the partition member 8, and the silicon melt in the raw material melting section flows into the single crystal growing section through the small hole 10. The lower edge of this partition member is fused to the crucible 1 in advance, or is fused by heat when melting the raw material silicon. 14 is a raw material supply device, which has an opening at the top of the raw material melting section,
Granular raw material silicon is supplied to the raw material melting section through this supply device. The supply rate is an amount equal to the silicon crystallization amount, that is, about 52 g / min. The raw material supply device 14 is connected to a raw material supply chamber (not shown) provided outside the chamber upper lid 16, and continuously supplies raw material silicon.

Reference numeral 15 denotes a heat insulating cover, which is made of a tantalum plate having a thickness of 0.2 mm. This suppresses the dissipation of heat from the partition member 8 and the raw material melting section.

In a silicon single crystal manufacturing apparatus according to an embodiment of the present invention configured as described above, a silicon single crystal growth experiment was performed. As for a silicon single crystal having a diameter of 6 inches, the graphite crucible had no opening. In contrast, when the graphite crucible has an opening, solidification from the partition member can be prevented, and the pulling speed of the silicon single crystal can be reduced, while the pulling speed cannot be increased to 1 mm / min or more due to solidification from the partition member. 1.1 to 1.3 mm / min.

FIG. 2 (b) shows another embodiment of the present invention. The opening 22 has a size corresponding to a range of 40 mm above the silicon melt surface and 5 mm below the silicon melt surface. That is, the number of the openings is 6 in a rectangular 45 × 200 mm opening. Also in this embodiment, the same effect as in the case of FIG. 2A was obtained.

[Effects of the Invention] Since the present invention is configured as described above, an amount of raw silicon corresponding to the amount of silicon single crystal pulled is continuously supplied, solidification is prevented from occurring, and a silicon single crystal having a diameter of 6 inches is prevented. The present invention has enabled high-speed pulling of a crystal at a pulling speed of 1.1 mm / min or more, and the present invention has great effects such as improvement of productivity and diversification of crystal quality characteristics by widening growing conditions of silicon single crystal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a silicon single crystal manufacturing apparatus of the present invention, FIG. 2 is a perspective view of a graphite crucible of the present invention, (a) is a perspective view of one embodiment, and (b) is another embodiment. Example perspective view, third
The figure is a graph showing the position above the silicon melt surface and the pulling speed of the silicon single crystal in an experimental example of the present invention. 1 ... quartz crucible, 2 ... graphite crucible, 3 ... electric resistance heater, 4 ... pedistal, 5 ... silicon single crystal,
7: Silicon melt, 8: Partition member, 10: Small hole, 14: Silicon supply device, 15: Heat insulating cover, 16 ...
... chamber lid, 17 ... chamber body, 19 ... outlet, 20 ... pulling-up chamber, 22 ... opening of graphite crucible.

Claims (1)

(57) [Claims] 1. A rotating quartz crucible containing a silicon melt having a sufficient depth, a graphite crucible supporting the quartz crucible, an electric resistance heater for heating the graphite crucible from a side, and the quartz In the crucible, the silicon melt is divided into a single crystal growing section and a raw material melting section, and a quartz partition member having small holes through which the silicon melt can flow, a heat insulating cover covering the partition member and the raw material melting section, A silicon single crystal manufacturing apparatus for pulling a silicon single crystal having a diameter of 6 ″ or more, comprising: a raw material supply device that continuously supplies a raw material such that the surface of the silicon molten liquid is maintained at a constant level in the raw material melting section In order to raise the silicon pulling speed to 1.1-1.3m / min,
50 above the silicon melt surface of the cylindrical part of the graphite crucible
An apparatus for producing a silicon single crystal, characterized by providing a plurality of openings in a circumferential direction from a position corresponding to mm to a position corresponding to 20 mm below the silicon melt surface.